Conventional alternators for vehicles include stator members and rotor members, together with rectifiers and other components, all mounted in a housing. The stator member is fixedly mounted in the housing member and the rotor member is rotatably mounted on a shaft inside the stator. One or more bearing members are used to facilitate rotation of the rotor.
Rotor members with claw pole designs have two pole pieces have claw fingers positioned around a rotor coil. The claw fingers of the two pole pieces are interleaved together in the rotor member and permanent magnets are positioned on, between, or adjacent the claw fingers and secured thereto. The rotor field coil comprises a wire winding on a bobbin.
The magnets in the rotor members are positioned to provide additional magnetic field sources that aid the field coil and prevent flux leakage between the claw fingers. The overall length of the alternator can be a primary consideration in the design and development relative to the particular vehicle and vehicle engine space requirements. In reducing the axial length of an alternator, however, sacrifices typically need to be made in the length of the rotor coil or in the stiffness of the claw fingers. Shortening the rotor coil can reduce the power output of the alternator, however, and lengthening the claw fingers may allow them to flex outwardly during high speed rotation and make undesirable contact with the stator member.
Thus, it is desirable to provide an alternator rotor member which does not reduce the power output of the alternator, or result in claw fingers which could contact the stator during rotation.